Can someone explain to me the satellite data? How does that work?
Plane was not subscribed to any data services, but it's equipment still sends out little "pings" that can be picked up by satellite. The pings are just the way for electronics to say "hey, I'm here if you want to talk to me". Cell phones work the same way.
In this case, there was a satellite in stationary (geosynchronous) orbit about 20k miles above the Indian Ocean. The pings from the jet evidently provide no data other than signal strength (i.e. very approximate distance from the satellite). Thus, they show that the plane was somewhere along a huge circle around the range if the satellite. You can cut some of that circle away based on how far the jet was fueled to travel, which leaves you with two big arcs - one curving NW into Asia and the other curving SW into the Indian Ocean. That's the best I understand it.